The total project detailed in the original application is directed toward four major aims which are summarized below: 1. To extract and purify virus-like particles with hepatitis specific serologic reactivities from human postmortem hepatitis B liver homogenates. To fractionate them into homogenous populations on the basis of size, shape and chemical composition. 2. To determine the serologic relationships among the various classes of hepatitis specific particles isolated. 3. To determine if among these classes of particles there are one or more which contain nucleic acid. 4. To characterize the nucleic acid containing particles with particular regard to the nature and properties of the nucleic acid and to their capacity for replication in tissue culture.